Commercial assay kits specificity validation

Finally, there are custom two-step quantitation methods such as chromatography or ELISA that require a capture step for isolating the protein and then a quantitation step based on a standard curve of the purified target protein. The preliminary capture step may also concentrate the protein for increased sensitivity. These techniques are typically not available in a commercial kit form and may require extensive method development. They are more labor intensive and complex than the colorimetric or absorbance-based assays. In addition, recovery of the protein from and reproducibility of the capture step complicate validation. Despite these disadvantages, the custom two-step quantitation methods are essential in situations requiring protein specificity. 

In the absence of an unambiguous history of ricin exposure, the preferred diagnostic method is specific immunoassay of ricin in serum, respiratory secretions, or other clinical samples associated with poisoning. Most of the methods described for ricin detection are experimental or are under development. The CDC and the Federal Laboratory Response Network have the capability to detect ricin in environmental specimens using validated polymerase chain reaction (PCR) tests and time-resolved immunofluorescence assays, with cell-based bioassays to confirm ricin activity. The U.S. Department of Defense has produced experimental field immunoassays, but commercial distribution of field test kits currently is limited. 

Method validation is a process that provides objective evidence that requirements for a specific intended use of the method can be fulfilled consistently in other words, that the method meets stated performance [7], Method verification (a term often used interchangeably with vahdation) is the provision of objective evidence that a given item also fulfils specified requirements [7], Together, these two processes underpin the evaluation of a methodology, which defines the analytical and chnical performance characteristics and ensures they meet pre-specified criteria. In the context of POCT devices, validation is likely to be undertaken once the device has been regulated and is available on the market. In most cases, commercial POCT methods will already have been vahdated by the manufacturer. These are the assay parameters that are often stated on the kit insert that accompanies the POCT device. The user (a laboratory in most cases), however, must independently verify that these characteristics can be reproduced locally. 

---